Introduction

For many people general overhaul of an old Quad amplifier may seem a useless affair. Through decades techniques have dramatically improved, so why not just buy a new amplifier? That is a misconception. Sure, there were many technical improvements but mostly for aspects like miniaturization and exchange transistors for IC’s. These developments facilitated mass production, but mass production seldom leads to quality improvement; all too often even to the contrary.

33 and FM3 revised versions

33 and FM3 seen from the back

Sure, many people possess that genial design of Peter Walker and Peter Baxandall, the Quad 33/303 pre/power amplifier combination (and the FM3 tuner, developed by Peter Walkers intimate friend and audio editor for Gramophone Magazine, Geoffry Horn) stored in a corner on the attic, collecting dust. But after refurbishment the combination is still a top rate HiFi system that can beat most of the competition and most of time provides a better sound quality as far as purity is concerned. Many music lovers who for financial reasons opted for refurbishment experienced to their astonishment that the renewed QUAD is audibly amply superior to most nowadays amplifiers.

After about 15 years of use performance of most electronics is deteriorating more or less. It’s difficult to recognize that deterioration as that process proceeds gradually. It is the same as in automotive. After a thorough check-up the car drives like new. The same process plays a role in audio electronics.
It makes no difference whether the equipment is intensively used or only on Sunday afternoon. Recently I obtained a factory fresh QUAD set in never opened cartons, stored for 40 years under the attic, but the set needed a total overhaul: withered capacitors, out-of-value resistors and corroded switches.
That is the main problem for the power amplifier, where relatively high currents are needed to feed the loudspeakers. The QUAD 303 design is the winner, thanks to the stabilized power supply, a thorough set up.
As mains voltage pollution is the topic now it is satisfying to ascertain that most mains pollution is absorbed in the 303’s design, where other companies bring costly mains cleaning ‘filtering’ units on the market. Quad 405 (306, 606 and successors) aren’t equipped with a stabilized power supply, just like countless Far East amplifiers. In those cases mains pollution finds its way through the amplifier. It is one of the many reasons why the 303 is QUADs best sounding amplifier. With nowadays wireless communication, countless small wall socket mobile chargers (rectifier units) in the home, the internet, Bluetooth and light dimmers in the home, the mains voltage carries a lot more frequencies than 50 cycles.

But as far as deterioration of electronics is concerned, after 15 years it becomes necessary to look after the dried up capacitors, many resistors out-of-value and it’s time for a general overhaul and the original alignments seems loose. 303’s unique feature is that all misalignments remain on the safe side, never in the direction of overcharge. Please note that when (most) power amplifiers lived for several years on the shelve, it is dangerous to switch the unit on; damage to both amplifier and loudspeakers could occur. Only a qualified technician can make arrangements to start the amplifier up again which can be done at very moderate costs!

We are experienced to solve problems with older QUAD equipment and that’s the reason that we can offer fixed prices for replacement of all parts of which we know that they need replacement. After overhaul the amplifier units and/or tuner are tested and distortion figures are measured. In case it becomes apparent that still certain parts have to be exchanged it will be done without price increase. Exception is made for mains transformers and for QUAD 33’s pushbutton sets. If replacement is necessary we will discuss that with the customer.

Why QUAD and no other brand? Quite simple, QUAD makes use of normal standard parts which are relatively easy to obtain or equivalents exist. Far East manufacturers every season release new models and or make alterations to the original design without notice and making use of newly and exclusively developed parts. That’s quite problematic as far as service is concerned also because service literature (if available!) doesn’t keep up with all the modifications. And after a few years those specific parts aren’t obtainable at all, or at extremely high costs. Several manufacturers – not the modest – simply throw away or even destroy spare parts after the legal obligation to give service for seven years. As mentioned before: most parts or equivalents for QUAD units are still on the market. And for few parts which aren’t obtainable at all, we developed other solutions, sometimes better than the original parts, such as the balance fader of the QUAD 44 preamplifier.

Refurbished 33-303-FM3

Let’s discuss the slogan ‘original parts’. Some European Quad representatives state that QUAD’s unique quality originates from exclusively selected parts. More manufacturers make the same claim. Nonsense! Of course parts are selected, most of the time more for price than for quality. QUAD often choose very cheap parts from several brands. So what’s original? Every QUAD aficionado knows about the low quality of 33’s original volume control as channel balance at low volume was a disaster. Not to mention the thousands of red brown block capacitors with aluminum instead of copper connection wires. But solder doesn’t attach to aluminum, so one could pull out those capacitors by hand. And then the always exploding Rifa spark killer on the on/off-switch which never was replaced for a better one!

Refurbished 405 power amplifier

Refurbished 34 preamplifier front view

The genial design of the 33/303/FM3 makes that the set is still in full swing and has less limitation in the choice and selection of parts. Needless to mention that better parts do give a certain improvement in operation; mainly nowadays better and smaller capacitors result in audible better sound quality. For refurbishing only first class parts are used: resistors are low tolerance (1 %) metal film types instead of the original high tolerance (10 %) carbon types. At the other side of the spectrum: gold labeled mil spec parts aren’t necessary as they do not improve the originally obtained optimum performance.

Warranty
A difficult chapter, warranty as far as older and used equipment is concerned. Only two components are excluded from warranty: the mains transformers and the QUAD 33 switch block. Guarantee has no time limit but we make proviso for the way the equipment was treated by the customer. E.g. in case a transistor is blown after two years, it will be replaced free of charge excluding transportation costs.

Please note: when you or your serviceman try to ‘repair’ cracking noise or interruptions with contact spray, please bear in mind that means is worse than the disease. In due course the pushbuttons stuck and the cracking noise is louder than before. Cleaning up the switches is time consuming, sometimes impossible and costly!

History and background: it all started with electronic valves

The QUAD II tube power amplifier is a very good unit, but apart of the output transformer, not that exclusive, although DNT Williamsons ideas about amplifying are still formidable. The mono block was sold at an affordable price. The Radford stereo valve power amp STA 25 (the mono version being the MA 25) was superior to the QUAD II and – rightly so – more costly. But that is more than fifty years ago. In those years I built several Radford copies by myself (2 x 15 Watts, making use of EL84 valves and Philips AD 9058 transformers). A sublime design.

Radford STA 25

Quad II

The valve Quad SC 22 preamplifier was connected with the power amp(s) with signal and several heavy power connecting cables. The Quad 22 is – as far as I know the only preamp capable of tenth of equalization curves, necessary for pre-RIAA and old shellac period recordings (at that time every record label had its own equalization). And yes, QUAD – not interested in innovation – maintained those correction filters long after they weren’t necessary anymore. The same applies for the Tape Monitor function, making use of external adapters and woefully inadequate. But the BBC used lots of QUAD 22’s in their studios for many years. In Europe it is not difficult to find qualified service for QUAD valve amplifiers, although the original QEC KT 66 power valves can be pretty expensive. One could always contact Quad Musikwiedergabe in Gering, near Koblenz (Germany) and in the Netherlands Willem Visser, Leiden (Gevamp Revisie), he is pretty active in the field – **31-(0)71 531 54 39.

Quad QC 22

AM Tuner

FM tuner

The dawn of a new age - transistors

The first transistor amplifiers appeared on the market in the sixties. Technicians kept them in high regard, but music lovers disagreed and rightly so! I remember very well that my technical friends regarded my home built Fidelio amplifier (Dutch DIY manufacturer Amroh – 2 x EL 84 – 10 Watts) as a prehistoric Flintstone-era design and found that its successor, the Amroh DIY semiconductor Robijn amplifier was by far superior.
And that Robijn was really a bad sounding amplifier as we learned in comparison. Much later we learned that crossover distortion, inherent to the first transistor amplifiers caused a vitriolic sound, mainly at low levels, but at that time technicians weren’t able to measure that type of distortion. It was one of the first problems that were easier audible discernable than measurable!

Amroh Fidelio II amplifier – courtesy Hein Beugels

Amroh Robijn amplifier – courtesy Hein Beugels

The Quad 303 power amplifier was one of the first semiconductor designs which sounded better than the QUAD valve amplifiers, even better than the Radford valve amplifiers.

Quad 50 and 303 power amplifiers

Much hailed in technical press are the famous QUAD 303 triplets and the simplicity of the QUAD 33 design. The set was introduced in 1967 and still is the best product Quad ever produced, apart from the electrostatic loudspeaker. After refurbishing the amplifier combination, it can compete without hesitation with nowadays high-end amplifiers..

The QUAD 33/303 combination was produced from early 1967 till the early eighties and in all those years QUAD was not interested in innovation. In fact that attitude was typical for all QUAD products. That’s a pity because certain limitations in the original design could easily have been solved in later years. At one hand Quad was very careful in design; at the other hand Peter Walker wasn’t interested in ‘minor details’.

It must be emphasized that the quality of QUAD products did not originate from components and production, but in the superior design philosophy of Peter Walker, Peter Baxandall and Mike Albinson. Therefore advertising with ‘original parts’ are laughable: thanks to the superior design even inferior parts did not deteriorate the sound to a certain extent. That better quality components result in better performance becomes clear after innovation by QUADREVISIE. Read in that regard Ross Walkers shocking comment in Ken Kesslers book “The Closest Approach”. A great book by the way, regrettably no longer available, but perhaps an antiquarian can be of assistance.

Book: Closest Approach

The Acoustical Mfg. Co. didn’t bother very much to innovate the QUAD 33/303 or the valve amplifiers. Later on, with the 34, 44 and 405 QUAD did improve dribs and drabs, influenced by certain bigger problems but – alas – most of the time inadequate, only depending on the availability or non-availability of certain components. Situation was even worse with the electrostatic loudspeakers.

One of the early limitations by setting up the QUAD 33/303 was the quality and capacitance of the electrolytics. The QUAD 303’s four power supply and output electrolytics @ 2000 microFarad couldn’t be bigger or larger, because they wouldn’t fit in 303’s housing. And that housing was identical to that of the 50E mono power amplifier, an exceptional product that came in production just before 303.

Quad 50

The Quad 50 mono power amplifier has the same size as the Quad II valve amplifier and in fact also the same concept in regard of the output transformer. And I still think QUAD originally meant the 50 to be the successor of the QUAD II. After lots of start-up problems with the first series, sales were stable but not enough to replace QUAD II. Then the 50E (and other versions) was born, the former design was redesigned to an universal amplifier for industrial and theatrical purpose of outstanding quality. As the 303 doesn’t make use of an output transformer, this stereo amplifier fitted perfectly in a 50E housing, which made the manufacturer happy.

The 50 series (with several variations to meet specific demands from professional users) and the 303 are almost identical as far as metal work is concerned. Instead of 50E’s massive output transformer, 303 is fitted with 4 large electrolytics. And between those the rectifier unit is mounted. Only one modification was realized during 303’s whole production history (1967-1984). At a very early stage: a new lay-out for both amplifier pcb’s was realized, not to forget that at a late stage the electrolytics were mounted upside down as a precaution. Before by defect, they sprawled down their aggressive fluid over both pcb’s, a costly affair.

Refurbishing and innovation backgrounds

All those 1967 design and production imperfections are improved by refurbishing the units. Although the original design concept is respected and maintained we catch up 303’s former limitations – say missed opportunities – as far as possible. The mounting metal rings for the electrolytics and the rectifier are now placed on an epoxy pcb, together with the stabilizer circuit, smartly developed by QUADREVISIE. Partly new wiring now can be thicker and shorter than before with direct connection from the pcb’s to both loudspeaker terminals and power transformer. Additional benefit is that cooling capacity for the three pcb’s is improved as free air circulation is easier than before.

Power supply unit 303 on chassis

Second step is a new – and by QUADrevisie developed pcb, mounted on the heat sink, on which the wiring of power supply – and power transistors are soldered. Doing so several problems of bad contacts or short circuits are eliminated.

Third step is to mount a new power stabilizing pcb, the former one always being blackish or semi burnt. The new pcb is also a Quadrevisie development using epoxy instead of pertinax. The new design shows little alterations to the original set-up.

Redesigned 303 pcb and the new pcb

Last but not least on both amplifier pcb’s the carbon resistors (10 % tolerance) are replaced by metal film types with 1 % tolerance just like the small electrolytics, adjustment potentiometers – and if necessary – other components on the pcb. These interventions are carried out by all refurbishment jobs on a 303.

Old and new stabilization pcb

Not only the stabilized pcb can be blackish but also both amplifier pcb’s. In that case they are also replaced by epoxy pcb’s, again developed by QUAD revision and updated to modern standards, impossible at the time of production. In that case both pcb’s are totally fitted with new components. These pcb’s are redesigned with heavier print connector tracks, so heavily loaded components get some more space, important for cooling.

Please find a survey below. Prices are standard, regardless of defects, including parts, labour and Dutch VAT. Only few exeptions are made – e.g. 405’s humming mains transformer. In those cases we’ll contact the customer by telephone or e-mail. Customers always can come by in Bavel, near Breda in the south of the Netherlands, even in weekends or in the evening. Just ring Armand van Ommeren on **31- (0)161 - 432451 or mail: armand@quadrevisie.eu for information or appointment. You’re most welcome.

Quad 33 Preamplifier

Introduction 1967
In production till 1982
Number of units 120.000 (figures obtained from Ken Kesslers outstanding book about QUAD history: “The Closest Approach”)
Sold in the Benelux countries: 11.000 units

Refurbished 33 preamplifier

New power supply unit for 33 preamplifier

The Quad 33 preamplifier can be regarded as the semiconductor successor of the valve operated QC 22, the last dating back to the fifties. Quite simple, but a delicate design, small and easy to operate. Characteristic detail is the famous tone/filter control, more or less copied from its predecessor. Distortion and noise figures are excellent even in the price bracket. Figures improve after refurbishing. There are certain limitations as far as the number of inputs (4) is concerned and the absence of a headphone output. We have solutions for both topics, see further on.

Redesigned pcb’s for 33 preamplifier

New power supplies for 33 preamplifier

Quad 33

QUAD 33’s volume control shows a relatively bad inter channel balance on low levels. That is true but also relative as the design philosphy states that little changes in volume ask for relatively big turn of the volume control so that room levels are obtained at about 70 % of maximum. It is also the fact that at the time of designing the QUAD 33 the output voltage of auxiliary equipment was much lower than nowadays, 100-150 mV became 0,5- 2 V. QUAD 33 ‘radio input sensitivity is stated as 100 mV, a cd player on that input could cause 20 x overload. That makes that the volume control at very low already results in a high listening volume. The nature of a logarithmic volume control (in contrast to tone control) is that correct inter channel balance is difficult to obtain at very low position. To overcome this problem QUAD 33’s total input sensitivity is brought back to 300 mV (Radio 1) and 500 mV (radio 2) while the S1 position of the DISC input is modified to the level of a CD-player (or iPod) and bypasses the Disc amplifier. Customer’s specific demands are easy to realize at this stage.

Who doesn’t recognize? Quad 33’s cracking and interrupting pushbuttons. As these type of switches (ITT Shadow) are not any more in production, it causes headaches to repair those switches, but early 2012 we found a solution to repair the switch units in order to make them o.k. for the next 25 years. We just interchange both pcb’s on which the switches are soldered by new prints with revised switches. In the same expedition we mount both adapters (disc and tape right on the motherboard to create space instead of the two little ‘doors’ at the back of the 33 for 2 sets of cinch connectors (disc and cd), just for convenience not to improve connection quality. We made that arrangement – although DIN connection is regarded as superior to cinch; cinch found its origin before the First World War! – to avoid the problems of thick disc cables, impossible to solder into small DIN plugs and because of the fact that every record player is fitted with cinch plugs and the use of adapter cables cinch/din can cause hum and inaudible oscillations and damage of loudspeaker tweeters.
Lots of users spend their money on expensive cinch connection cables for their cd-players. Both adaptors stay in use, but can only be regulated by a technician, but luckily that is nowadays not necessary anymore.

Quad 33 with cinch connectors (aka RCA, Revox or tulip plugs)

Much in demand: a Quad 33 fitted with cinch connector instead of DIN. Standard answer is that DIN connectors are superior and more reliable. Apart from that re-arranging the back panel for cinch would become too costly and is – as far as QUADrevisie is concerned – out of the question. But we are down to earth and realize very well that it is practically impossible to get a thick and costly cable into such a small DIN plug. To meet the demand we made arrangements that both cd- and record player can be connected through cinch.

The Disc-input is directly connected to the cinch inputs. Radio 2 input – mostly used to connect a cd-player is connected to an extra cinch input including an attenuation circuit. That means that Radio 2 has the same input sensitivity as Radio 1 input, doubling with a cd-input on cinch but with al lower sensitivity to cope with most cd-players, iPods, DACs and the like.

Prices:Refurbishment Quad 33 preamplifier € 195,- all-in

- Renewal power supply pcb including all electronic parts
- Renewal mains filter
- Replacement of all electrolytics and lapsed resistors
- Exchange all semiconductors by new ones
- Necessary replacement of volume and balance controls
- Modify Disc-adapter to CD-player/iPod function on S1, saving the disc function
- Attenuation of Radio 2 input for CD/iPod

Total overhaul including new pcb’s and switch sets € 375,-- all-in

Refurbishing a Quad 33 preamp including cinch inputs € 100,-- extra

Detail Quad 33

Detail Quad 33

Quad 33 preamplifier new version

The Quad 33 preamplifier originates from the pre sixties and came into production in 1967. After minor modifications the unit found its definite form and stayed in production for about 15 years. Successive models like the 44 in 1979, the 34 in 1982, are more versatile and/or present the famous tilt tone control, but 33’s sonic capacities are superior, apart from the first production runs of the 44, practically identical to 33. All later models audibly present more ‘clarity’, most of the time appreciated by listeners, but turn out to be specific and tiring-to-the--ear distortion.

Problems? Solutions?

I am still astonished to read about technicians who totally rebuild the Quad 33 and make it a completely ‘other’ amplifier, but never discuss 33’s primitive pushbutton sets with their complicated functions. Both 33’s pushbutton sets – source selection and tone control - aren’t available for many years and also the separate Shadow series F pushbuttons are out of production. To make matters worse the source selection pushbutton set is interlocked between two pcb’s. It is not possible to remove the set without damaging the pcb’s. We solved that problem a few years ago by copying the upper pcb in an improved form and from better material. (see picture). Alas, fundamental problems with the switch sets are not solved, but it is now easy to remove the small pcb the switches can be cleaned.

Too late

For many pushbuttons it’s too late as they are too weared out and repair is not possible anymore. There’s one labour intensive solution with great risk of damaging the mother pc board. Apart from that: Quad 33’s switch routing is extremely complicated, some functions are routed over six switches which causes too much transition resistance. That can result in interruptions in one or both channels, very disturbing and stubborn. Selecting new switches caused headaches. Electronic switches as used in 34/44 were also problematic, new prints fitted with relays (space and current consuming) or buying old 33’s to remove good working pushbuttons etcetera.

New developments

1 – New switches
To solve the well-known difficulties with Quad 33 switches, we developed new pcb’s and new switches. In that case the complete 33’s electronics are interchanged with new one, but maintaining Quad 33’s unique sonic qualities and with conservation of the Tape and disc adapters and front view of the 33. Many 33’s little problems are now eliminated e.g. the complicated switching circuitry and the mono/stereo function. For certain input selections about 6 switches work in series which easily can cause interruptions. In the new set up always two switches work in parallel and the mono/stereo function is improved by pushing MONO > the right channel appears on both channels and by pushing < MONO the left channel appears on both loudspeakers. By pushing both mono switches the mixed lift/right channel appears on both speakers. Alternating between both mono switches and the stereo button can give an indication of the amount of spaciousness in the recording as real stereo recordings (and not so called phase coherent or compatible recordings) sound duller by switching on mono because of extinguishing of higher frequencies.

Totally new pcb’s with switch units for Quad 33 preamp – but faithful to the original design

Tone control switches are also exchanged for new types and mounted on a new pcb, including new electronic parts, also including 2 small plug-in new preamp boards.

Quad 33/2 Preamplifier

A few ago we were puzzling about a totally new set-up of the Quad 33’s pcb’s and connection boards. As always such improvements take their time because every step asks fort a step further on.

A completely new setup for Quad 33’s back panel with cinch instead of DIN -connectors doesn’t make sense, not only as DIN connectors are superior to the always cracking cinch type, there are fairly much better and more reliable connectors (e.g. XLR, Neutrik). It is bizarre that the audio industry worldwide sticks to those lousy cinch connectors, neglecting better and far more reliable alternatives. But it is worthwhile to fit extra cinch inputs for CD and Disc to avoid cinch/din interconnects and to facilitate the use of thicker cables who won’t fit into a relatively small DIN -plug. Only for those reasons we made that arrangement, not for improving sound quality by use of exotic and expensive interlinks

Input sensitivities

Also bizarre in my opinion is the extremely high input sensitivity of nearly all amplifiers even the so called Hi-End ones. Expensive en costly designs seem more important than ease of use and adequate. Input sensitivities of 100 mV and even 50 mV are no exception and far beyond reality. Ten to twenty times over-sensitive shows no feeling with real world circumstances, perhaps conducted by the marketing department! Already by refurbishing the 33 preamp by QUADrevisie all input sensitivities were taken back to realistic proportions by fitting attenuators on Radio 2 input and on the S1 position of the DISC adapter. Both attenuation circuits are now part of the mother pc-board. Also the gain factor of both ouput amps were taken aback in favour of better noise figures and optimum settings of the volume control. It is ‘normal’ when room volume appears at 70 % of the rotation of the volume control. Both preamp plug-in cards of the 33 are newly designed to cope with the dimensions of modern parts. The same counts for the DISC plug in card. All these plug-in cards can be used in the original 33 preamp in case they have to be replaced for whatever reason. The power supply pcb was already newly designed for bringing up the supply voltage from 12 to 16 Volts. Doing so all 33/2’s prints and parts are new, apart from the mains transformer.

Disc and Tape Adapters
In the original set up two plug-in cards were accessible from the exterior, On those cards the sensitivity input/ouput for TAPE and for Disc the input sensitivity could be chosen. Although a practical solution at the time of introduction it is nowadays without meaning.
Disc input sensitivity on 33/2 now can be regulated through two so called DIP switches next to the Disc amplifier card, accessible by unscrewing the housing for a few centimeters, to select between M1 and M2 (the C1 position is abandoned). While the S1 position is now provided through a switch at the back.
Tape in- and output sensitivities are in fitted positions now as it is no longer necessary to make them adjustable. For those with special demands we can make any arrangement in that field.
Eliminating both plug in cards made room for two sets of cinch inputs (DISC and CD) a provision that will make regular 33 users very happy. The CD cinch input is directly connected to the AUX/Radio 2 input, although – as mentioned before – attenuated to a realistic value.

All chassis inputs are renewed and replaced by metal DIN inputs and gold plated cinch inputs.

Switches

In the original pushbutton switching diagram switching from one to another input was very complicated with extensive routing of the signal, over many contacts resulting in lots of problems over the years. Many technicians tried to solve the problems with more or less success, but very labour intensive and thus costly. So we found a better solution.
Those switch sets are not available any more for many years and the sets available won’t fit onto the pcb because of a different soldering pin pattern. Besides, most of the time removing of the old sets will damage the pcb. More important we would like to get rid of the complicated switching procedure and designing new prints would also facilitate new soldering patterns for the new switches. All welll that ends well, so to say!
By realizing switch functions in parallel instead of in series would boost the reliability enormously. The three orange pushbuttons for mono-left, mono-right and stereo, but the functions are altered, see above. The tone control’s three potentiometers are now from first class Swedish make and all internal signal cables are screened to avoid RFI (radio frequency interference). Switching between AUX2/DISC is realized at the back of the preamp. Most music lovers use the record player not every day, the player stays connected to the 33 and be activated to turn the switch. On request we can alter the DISC input into an extra line input for iPod or DAC.

Price € 685,--

New manual – only in Dutch

As most users lost the original user’s manuals, we realised new manuals for both the original Quad 33/303/FM3 as for the newly developed Quad 33/2 and Quad 303 QR and 405. This combined manual is standard supplied by every set sold. For those who want to orientate or complement their equipment already in use, the new manual is available at € 10 excluding p&p). Reimbursement at the moment you buy a new set. The making of an English version is possible when there is demand.

Wooden cabinet for 33/FM3

Dutch loudspeaker manufacturer Hepta can supply a remake of the famous B333 to house both Quad 33/2 and FM3 in real and oiled oak finish, but other finishes are available upon request.
Price for the cabinet excluding shipping costs € 150,--
Price a the moment of refurbishing or buying a new set € 100,--

It is also possible to manufacture a wooden cabinet for Quad 34 and FM4, please refer to QUADrevisie.

Quad 303 Power amplifier

Year of Introduction 1967
In production till 1985
Total units manufactured 94,000
Sold in the Benelux: about 13,000 units
A small series of 303 in the new grey colour was produced at the end of the production cycle to cope with the Quad 34/3030 colour.

Refurbished 303 latest edition

Original 303 before refurbishing

The Quad 303 is widely regarded as the best power amplifier Quad ever produced. Sounds great, unconditionally stabile with any load with practically unlimited life expectancy. It only needs some minor servicing once in twenty years, that’s all. A genial design that never loses its original high quality and it still stands the test of time.

Original wiring for 303’s heat sink

New pcb for 303’s heat sink

New heat sink print wired and connected

303’s Original pcb’s before refurbishing

Perhaps good to mention that amplifier technology did not really progress since the introduction in 1967 of the Quad 33/303 concept. Sure lots of components have improved both in quality and in specification, but the sound quality did not improve, in fact detoriated, because much attention slipped away in extras like functions, miniaturisation, gimmicks, multi channel and the like.
And by refurbishing the set, the 33/3303 combination gains by the bettter quality of nowadays parts: capacitors, metal-film resistors and the like. Regrettably most nowadays audio equipment is fitted with inferior integrated circuits and IC switch circuitry who don’t improve overall sound quality. All fuzz about ‘much better’ torodïal power transformers is in fact reprehensible as normal EI transformer do their job equally well. It only depends on a thorough design, not squared up by the penny pinching marketing department.

Original 303 driver in bad condition

Old and new 303 driver PCB’s

Old and new 303 stabilizing PCB

Brand new 303 driver and stabilization PCB

Note: there are more technicians around the Benelux who offer to improve or renew the 303. But caveat emptor (beware) because in some cases the amplifier is rebuild to a complete different design. The ingenious concept is altered into a push-pull amplifier and also the power-supply (certainly a most essential aspect of the 303) is rebuild. This approach misjudges 303’s original quality and leads to a less good result. In this case one could say that you cannot speak of a 303 but of a different amplifier design. Nice perhaps but it has nothing familiar to the original design concept. I stick to the original setup and leave the 4 pole DIN input as DIN connection is superior to that of RCA/Cinch/tulip. Only for the 33 preamp I make an exception for certain inputs to avoid the wellknown problem of DIN/cinch interconnection cables.

303 back to the basics with newly lacquered transformer

303 driver PCB

Refurbished 303 driver PCB

Refurbished 303 chassis with new PCB’s

Aligning refurbished 303 circuitry

And here it is: the renewed 303

The three PCB’s at the bottom of the 303 are mounted with plastic clips. Those clips cannot stand the test of time and become bros and sometimes they are broken. Those clips aren’t available anymore and sometimes they are interchanged by tie wraps. I regard that approach as risky as it can result in short circuit. When necessary and by complete refurbishing of the 303 QR the pcb’s are screwed on newly developed plastic strips.

N303’s new power supply on chassis

3030’s new input and PCB including LED instead of neon light

Refurbishing Quad 303 power amplifier Option I: (€ 275,--)

- Cleaning , disassembling en lacqering of the power transformer
- Exchange power PCB by a newly developed PCB with both new electrolytics and rectifier
- Mounting an newly developed PCB on the heat sink
- Exchange the power stabilisation by a new one with new electronic parts
- Exchange all resistors by metal-film ones and most capacitors on driver PCB’s
- Customise outputs’ wiring
- Alignment and measuring distortion and S/N-ratio

Complete new set PCB’s for 303

Newly developed power supply for new Quad 303

Option II (€ 395,--)

Some Quad 303 power amps are heavily used through the decades (!) or had too less ventilation. In those cases both driver print boards became too warm and it is necessary to replace them. It would be useless to mount the old parts on new PCB’s so all components are interchanged. In that case one could speak of an ‘new’ amplifier, only the housing and the mains transformer date back to the original production year.

Some customers want better loudspeaker outputs and like the possibilily to connect the power amp throug RCA/cinch inputs. In that case also the Bulgin net-entry is replaced by the European IEC power input in combination with on/off switch . The voltage selector is left away, if necessary another mains voltage can be chosen by an experienced technician by resoldering the mains transformer input.

Cables

For sale: refurbished Quad 303 power amplifiers

Standard refurbished Quad 303 power amplifiers € 375,--
Original housing, original PCB’s with largely new components, newly developed electrolytic/rectifier/stabilization and heat sink PCB’s , aligned for general issue or restricted for Quad ESL 55 electrostatic loudspeakers, including signal- and mains cables* and instruction booklet.

Refurbished Quad 303 power amplifier with new driver PCB’s € 475,--
Original housing, newly developed electrolytic/rectifier/stabilization and heat sink PCB’s, new driver PCB’s fitted with new components, aligned for general issue or for Quad ESL 55, including cables* and instruction booklet.

Quad 303 QR power amplifier with new drivers and new connecting panel € 575,--
Original housing with new front (see picture) and connectors, newly developed electrolytic/rectifier/stabilization/heat sink PCB’s, new driver PCB’s fitted with new components, aligned for general issue or for Quad ESL 55, including cables* and instruction booklet.

Quad 303 QR power amplifier, housing in newly sprayed painting with new connecting panel € 675,--
Newly paints prayed housing with new front panel and connectors (see photograph), newly developed electrolytic/rectifier/stabilization/heat sink PCB’s new driver PCB’s fitted with new components, aligned for general issue or for Quad ESL 55 loudspeakers, including cables* and instruction booklet.

* Cinch or DIN of your choice

Quad 303 QR power amplifier

In recent years a stock has been built up from defect 303 power amps with the intention to refurbish them to nowadays standards. The original metal work has been painted somewhat more greyish as the original colour has darkened through intense decades in use...

303 QR

303 QR

A new chassis has been designed, and really all PCB’s are brand new. A new connecting panel has been fitted including IEC mains input/switch, new – and wider spaced gold plated loudspeaker outputs and a 3 pin DIN input doubles with RCA inputs.

3Building up Quad 303 QR

Complete set of PCB’s for new 303

Voltage selector has been removed. If another mains voltage is necessary a qualified technician can make in a minute the necessary arrangements internally.

We chose for a 3 pin DIN-input because the original 4 pin DIN connector caused confusion: it was possible to plug it in wrongly. Replacing the 4 pin DIN by a 5 pin type is not advisable as accidentally tape output plug can be plugged in direct to the power amp which could result in blown up loudspeakers.

Quad 50E Mono power amplifier

De Quad 50E Mono power amplifier is specially designed for universal industrial/professional purposes e.g. in studio’s, public address systems and 24/24 use under extreme conditions. (not in a living room)

Input is universal with a 0-500 mV input sensitivity while the output serves 4-200 Ohm loads. The amplifier is absolutely stable with any load. You’ll find a detailed brochure under the heading Quad information on this site. Although the 50E can be used as mono block in a stereo set-up or as power amp for public address, it must be emphasized that the use of an output transformer – as in the 50 E – sets the lower limit of harmonic distortion at 0,1 %. That’s inferior to Quad 303’s THD (total harmonic distortion).

Quad FM2 hybrid tuner

Introduction 1968
In production till the end of 1971
Total produced 7.500
Estimated: a few hundred units sold in in the Benelux

Quad FM2

Quad FM2

In fact the old valve operated FM1 unit with - at that time - a separate semi conductor multiplex unit, fitted in a Quad 33 style housing. The separate stereo decoder was a cause of trouble which also counts for the FM2 decoder. Main problem – and nearly incurable - is mechanical wear of the dial coil (instead of a dial capacitor). Only touching the dial knob makes the tuner drift away. Later FM3 tuners are superior to the hybrid FM2 (partly valve, partly semiconductor operated). The preference (if any) for the use of valves in this stage of the tuner has really no Hi-End meaning, whatsoever.

Quad FM3 Tuner

Introduction 1971
In production till 1982
Total produced 50,000
Estimated number of units sold in the Benelux 3,000

Quad FM3 detail

Quad FM3 detail

The FM3 tuner can be regarded as one of the best tuners of its time. The tuner is better equipped to derive most of the FM transmitters in Europe’s crowded FM band and does the job better than the over sensitive tuners, developed in the Far East. One minor disadvantage is the low stereo pilot tone suppression (19 and 38 KHz) but even most discerning listeners won’t hear that. In some cases that disadvantage resulted in interference – an audible wistle tone - with tape or cassette recorders bias frequency (@ 95 kHz). But all Dolby cassettedecks – if in use! – are fitted with an MPX filter to solve that problem.

Quad 33-FM3

Quad 33-303-FM3

Refurbishing the FM3 means renewal of the power supply and of scale light and of the two fine tuning bulbs. A non-problematic tuner, so to say. The first issues are equipped with the old - and no longer available - MC 1305 decoder IC. Redeveloping to the new and definite MC 1310 IC phase locked loop decoder, as applied in later FM3 versions, is not possible.

Quad AM3 AM-Tuner

Introduction 1969
In production till 1973
Total units manufactured 2,000
Only a few dozen sold in the Benelux- collector’s item!

Quad AM3 en FM3 tuners L1030318

This tuner seldom occurs and some aficionado are on the outlook for several years. A valve operated design produced in two versions, the European version (long- , medium and shortwave) and an ‘Overseas’ model (medium and 2 x shortwave). The electronic valves are on the shelve everywhere and a low cost overhaul is upon request.

Quad 44 Preamplifier

Introduction 1979
In production till 1989
Total units produced 40,000
In Benelux countries estimated 5,000 units

Refurbished 44 preamplifier

Back view refurbished 44 preamp

Opinions about 44’s quality differ. Some functions are confusingly set up, e.g. both tape monitor functions can cause howling. Also the balance/mono function can raise eyebrows. Quad produced a number of mark ups, concerning connections, filter positions and outlay. The latest version is most attractive thanks to doubled cinch/din connections, but more important is the motherboard’s improved layout and also that the tone control ‘Tilt’ was modified from two to three positions up en down. And those modifications made this 44 desirable above its predecessors.

Some 44’s suffer from spontaneous switching from one to another input. Quad made modifications to solve that problem, but that didn’t work out. But in fact it is not that difficult to solve the problem, also for Quad 34. Also problematic is the balance control for both preamps: really too fragile. That part is not available anymore and will be replaced by a new fader with a special pcb, but that’s not visible on the front panel!

Much mentioned is the fact that at #1 of the volume control already sound is audible. That makes exact volume control for background music difficult. In fact it is not the volume control that causes the problem but too sensitive inputs. For us that problem is easy to solve and free of charge in case of a standard overhaul. But it is always possible to make that modification later.

The balansfader of the Quad 44 often cracks and interrupts and can’t be replaced as the original part for many years is not available anymore. That’s why we made a PCB to replace the switch and the fader for a type that is available. In case of refurbishing this is done for € 50 extra – without refurbishing for € 100

New linemodule (CD, DAC, iPhone, etc.) for Quad 44 pre-amp

Difficult to get are input modules Radio, AUX and CD for the Quad 44 pre-amp. Now we offer new modules with DIN and cinch connections and high end Burr Brown OPA 134 IC’s. Price: € 150,— each.

New linemodule

New linemodule

Refurbishing Quad 44 preamplifier (all versions € 195,--):

- New power supply electrolytics and resistors
- New electrolytics throughout
- Replacement of nickel inputs by gold plated versions
- If necessary: replacement of balance control
- Repair of p.c.b traces and switching problems
- Replacement mains filter/spark killer

New linemodule for Quad 44 pre-amp: € 150,--

Quad 405 power amplifier

Year of introduction 1975
In production till 1982
Total build 65,000 (presumably incorrect, up to serial number 59,000 the amplifier was called 405, above serial nummer 65,000 is was called 405-2).
Sold in the Benelux countries: estimated at 8,000

Refurbished 405 power amplifier

New power supply in 405

Successor of the 303 amplifier. Was it marketing that asked for ‘something new’ or the wish for more power? The scene asked for gigantic power amps, sometimes 1,000 Watts per channel. And a new design without need for alignment would make life comfortable for Quad isn’t ?

The Current Dumping principle on which the 405 is designed is impressive but audibly the 405 sounds inferior to 303. Only the latest versions of 405-2 came in quality near to the 303 concept. But 303 stays at the top!

On the newly developed pcb’s to house the electrolytics we reserved space to mount the crow bar loudspeaker protection as – in case of trouble – it is cheaper to blow up power transistors than costly loudspeaker units. Earlier 405’s (prior to serial number 9000) weren’t fitted with that useful device and we build it in automatically in by refurbishing. Also attemps of the manufacturer to mount that device on the loudspeaker terminals (serial number 9001 and higher) will also be removed .The 405-2 has a better solution for mounting the crow bar (on the amplifier pcb).

405’s power supply including loudspeaker protection

Each 405 is fitted with new loudspeaker connectors

More and more first issue 405’s have detoriated printed circuit cards, most of the time due to the extreme high working temperature and lack of any internal ventilation. To solve that problem we designed new amplifier cards, based on the 405-2 which results in an audible improvement in quality.

Refurbishing Quad 405 power amplifier standard price € 195,--

- New power electrolytics on newly developed pcb
- Mounting the crow bars on old type 405’s
- Moving the protection unit from loudspeaker terminals tot pcb
- Replacement of out-of value resistors
- Replacement of all electrolytics on amplifier boards
- Replacement of loudspeaker terminals by gold plated connectors and – if necessary - also for the input connector

Modifying Quad 405 to Quad 405-II

Many older Quad 405’s (up to serial number 59.000) with amplifier boards……….. Replacement of those boards isn’t useful nor possible. It is far much better to mark up the amplifier to 405-2, using the M12565-7, one of 405’s later versions of the boards.

Brand new amplifier board for 405-II

EAn ‘old’ 405 board

Rebuilding the 405 means that all components on the boards are replaced, even the power and driver transistors resulting in a real 405-II: an amplifier which also can better cope with low impedances, one of the disadvantages of the original 405 design.

Rebuilding the 405 to 405-II with both amplifier boards

New connectors and power supply (on the right the right amplifier board)

In and outputs are replaced by better fitted to-the job types while the loudspeaker protection found space on the amplifier boards.

Quad 405-2 power amplifier

Year of Introduction 1982
In production till 1993
Total units produced 100,000 (presumably incorrect, must be 41,000 ; on a total of 100,000 units, 59,000 were 405’s and 41,000 405-2’s)

Power unit board 405 including crow bar protection

New 405-2 next to the old 405-1

This one is superior to the old 405 and next to 303’s quality who stays winner! Those who want or need more power it is better to use a 405 -2 than bridge a pair of 303’s to obtain a 100 Watts.

New 405-2 unit

Power supply unit 405-2

Refurbishing Quad 405-2 power amplifier (€ 195,--)

- New power supply electrolytics on newly developed board
- Replacement of out-of-value resistors
- Replacement of all capacitors in the amplifier
- Replacement of loudspeaker terminals for gold plated connectors and if necessary also the DIN input connector

405-2 after refurbishing

Each 405 is fitted with new loudspeaker gold plated terminals

Quad 34 preamplifier

Year of introduction 1982
In production till 1995
Total units built 41,000
In Benelux countries estimated at 7,000

Line input module Quad 34

Refurbished 34 preamplifier front view

Basically the same design principle as for 44, but different in lay-out: all components on one mother board. In the first production runs fitted with very bad light blue electrolytics, about 20 pieces. They tended to leak and demolish the board. These capacitors must be replaced by precaution to avoid incurable problems with the mother board. When these problems occur the 34 changes – just like the 44 – spontaneously from one input to another. Typically British: ‘penny wise, pound foolish’ as far as the choice of parts is concerned. A comparison with British automotive industry is apparent.

Refurbished 34 preamplifier viewed from the back

Special Quad 34 Line module in place of the Disc module

All those problem signalized above are being replaced just like the balance control which is really too fragile. That part is not available anymore en will be replaced by a rotating control, or a new fader on an new pcb.

For those who don’t play gramophone records, a line module is available which makes the 34 a four input preamplifier.

Refurbishing Quad 34 preamplifier (€ 195,--)

- New power supply electrolytics and voltage regulator
- Replacement of all capacitors and out-of-value resistors
- Exchange nickel Disc input by gold plated ones or by a line input module (+ € 25,--)
- If necessary: replacement of balance control
- Repair of pcb-traces and switching problems
- Line input module instead of Disc input module, € 50,--

Difficulties with the Quad 34 preamplifier

The Quad 34 preamplifier –introduced in 1982 – a real nice design for the real avid music lover: rather elementary in set-up but meeting exactly the demands: four dedicated inputs (DISC input can by changed in a line input by QUADrevisie). Also the tone control functions in a musically highly desirable way (amplifiers without tone control do not meet the real world demands of a music lover). The 34 combines a very low distortion with utterly simple operation.
Armand van Ommeren

Nobody will be astonished that minor difficulties occur after 30 years of y use. And it is not realistic to complain about those Quad people in Huntingdon/England for the low building quality standards which is partly true, but on the other hand, when the majority of the Quad units do their job flawlessly for more than 20 years who can blame the manufacturer: the majority of the competition does not last that long. In short: no reason to complain.

Alternatieven?
As mentioned in the introduction, it is worthwhile to investigate the problems and how to solve them! And what can be the alternatives and they cheaper or more expensive apart from the sympathetic dimensions of the 34?

Wat zijn dan de problemen met de 34? Alternatives?
There aren’t: not only preamps with a comparable simple and musically near perfect tone control don’t exist, but all possible alternatives are at least as old as the Quad 34 and suffer from more or less the same problems as the Quad 34. Preamps now on the market don’t offer that facilities.

Quad 34’s difficulties
There are seven issues of the 34 ; the service literature only describes 5 versions. In all versions the whole amplifier is built on one mother board with all components fitted on it. It is a two sided board with about 80 connections between top and down. These connections tend to rust. Rust doesn’t conduct at that causes interruptions. First editions were fitted with very bad light blue electrolytics, about 20 pieces. They tend to leak and demolish the board. These capacitors must be replaced by precaution to avoid incurable problems with the mother board. When these problems occur the 34 changes – just like the 44 – spontaneously from one input to another. Typically British: penny wise pound foolish as far as the choice of parts is concerned. A comparison with British automotive industry is apparent.

Quad 34 interior view with green lacquer laying, version 5

By versions 5 and 6 the top of the board is sprayed with a light green lacquer to solve the rust problems. But the lacquer corrodes the copper print tracks – apparent in black rash thus causing new interruptions; the remedy is worse than the problem.

Detail picture of wethered print tracks below the lacquer layer, also giving a good impression of the problematic rusted print through interconnectors.

Less problematic is that different brands of IC’s were used, with different characteristics sometimes also causing spontaneously switching of the inputs. And last but not least the balance control ……

How to solve…?
DProblems increase through the years. Many Quad 34 preamps were refurbished but often the old problems appeared again, a process – regrettably – with no end.

Quad 34 with orange logo

The only relatively up till now trouble-free version is #7. Dat version showing an orange Quad logo on front seems not problematic. I write ‘seems’ as I have serviced Quad 34/orange logo, fitted with a version 5 pcb and I also saw 34’s with the #7 pcb but no orange logo on front!
The only way to radically solve all problems is to interchange the complete two sided mother board by a new one of perfect quality. So it was necessary for us to develop such a new mother board giving us also the opportunity to rearrange the wiring for the balance control to facilitate instalment of a new control. Also mains filtering is modified and improved. The wellknown ‘flags’ for attenuation of the inputs are interchanged with more reliable dipswitches. The new board facilitates both DIN and Cinch inputs but leaving DIN inputs away in favour of Cinch types is in fact nonrealistic as DIN is superior to cinch. All interconnecting cables are available on request.

Quad 34 interior with a fine motherboard, version #7

What are the costs?
Developing and realising a new mother board – an adapted version of #7 is an enormous undertaking as the mother board carries about 300 components! We can reinsert the mains transformer and – switch, the bass, tilt en volume controls and a new balance control. All other parts are brand new: resistors, capacitors, diodes, semiconductors, IC’s and dipswitches. Apart from some parts and the housing one could speak of a complete new Quad 34.

We estimated the costs for rebuilding a Quad 34 at € 475,--. An instruction sheet how to work with dipswitches is supplied.

Adapting the Quad 34 tape button
Quad 34 tape function differs from the other line inputs. When the Tape button is pressed the original source stays active. That was necessary for three head cassette- and tape recorders to facilitate monitoring without interrupting the original source. This function is useful to check audibly the quality of the recording in progress.

But who works nowadays with a tape or cassette recorder and many Quad 34 users are more interested in a line input than in the monitoring facility. QUADrevisie can arrange that by small surgery in the electronics. A small pcb is mounted on the button board making the Tape function work like a normal line input.

Extra costs € 50 by refurbishing. Exclusively € 100

Quad FM4 Tuner

Year of Introduction 1982
In production till 1995
Total amount produced 37, 000 units

Refurbished FM4 tuner

A relatively good tuner, but not digital. It’s an analogue tuner with digital read-out and presets. Often leakage from the accu which can be replaced by 3 penlites good for 8 years of working life. Just like the 34 preamp problems can occur with the power supply and mother board. Slightly problematic this tuner: the FM3 is not only better but far more reliable.

Price overhaul, dependent of the state of the tuner
Quad FM4 tuner overhaul standard price € 125,--
For building in a battery holder instead of the accu 25,--

Quad 66 system

Year of introduction 1989
In production till 1996 (CD66 till 1993))
Total amount of production 12,000 (tuner 5,100)

The Quad 66 system with the remarkable Scepter remote control (paying homage to B&O’s much smarter design) was not long in production, due to lots of setbacks with the cd-player as Philips discontinued the production of the laser unit and also the tuner became problematic due to difficulties in the supply of Telefunken IC’s. To make matters worse the production quality was not up to standard. I’ll try to solve persistent problems – investigation at no costs – but I cannot offer an overhaul.

Quad 606 power amplifier

Year of introduction 1986
In production till 1997
Total amount of units produced 27,700

To meet the demand of more power to the music, Quad devised in 1986 the 606, as a brother for the 405-2. The difference in power output is not very much – about 40 Watts @ 8 Ohms – making use of the same Current dumping principle as the 405-2 but sounding slightly inferior to his brother. Gain in power, compared to 405-2 is practically negligible so at the end an well working, reliable amplifier results, but I was not impressed by its sonic qualities.
Note: at the time I was reviewing the 606 for the authoritative magazine Benelux Luister, I really was enthusiastic about that set. I listened to ESL 57’s connected to my own 405 (first series). I then went over to 606 that appeared to be the winner. Later on I got a Sony integrated amplifier TA-FA7 (about 2200 euro at that time) and that amplifier sounded far much better than my Quad 44/606 combination.

A few years ago I could lay my hand on a sympathetically priced second hand Accuphase C200-V preamplifier (I was always fond of their preamps, tuners and cd-players). To combine the Accuphase with the Quad ESL 988 in my room, I temporarily made use of a refurbished Quad 303. The difference with the Sony block then in use, was incredible. Far much better defined low frequencies and overwhelming and sparkling mid and high (strings, voices).
I was astounded. Since that time several of my clients reinvented the qualities of the 303.

Quad 306 power amplifier

Year of introduction 1986
In production till 1995
Total amount produced 25,000 units

The belated successor for the 303 power amplifier, but without 303’s intrinsic qualities. In fact the 306 and 606 (and also 707 and 909) are built according to 405’s Current Dumping System and ‘ínferior’ to the 303. They appear to sound crummy in higher frequencies (the 405-2 being superior to the other types) and hyper sensitive to their respective power supplies. After a short time the shortcomings of the supply electrolytics become discernable. They are all amplifiers without a stabilized power supply, apart from the 303 and that amplifier is therefore less sensitive for mains pollution and I wouldn’t be surprised that all mains supply pollutions from rectifiers and the like have their influence on the performance of an audio amplifier, mainly not suppressed by good power supply in the amplifier. Strangely enough nowadays more attention is given to expensive mains filtering than on a thorough design of an amplifier’s power supply.

An overhaul includes replacement of the power supply electrolytics and of small parts. Also the loudspeaker connectors are subsistuted by better ones.

Overhaul costs depend on the state of the amplifier, standard price € 125,--

Quad ESL electrostatic loudspeaker

Year of Introduction 1955
In production till 1985
Total number of speakers manufactured 54,000

Peter Walker spent a great deal of his life on development work on loudspeakers to begin with cone loudspeakers combined with ribbon tweeters, but he soon focused on electrostatics. Quad’s first ESL was just named Quad Electrostatic Loudspeaker without type number. But because the ESL 63 was numbered after the year of invention, the manufacturer gave the old type the number 57. In fact not correct as that development started in 1955, so 55 would be the right denomination.

New built en refurbished ESL 57 (also grills and legs!)

New built ESL 57

THE ESL concept was not the first attempt, undertaken by Peter Walker to build a ‘better ‘ loudspeaker. You can read this line bearing in mind that he – Peter Walker – was not content with existing loudspeakers on the market in those years. For many years he was experimenting with corner ribbon loudspeakers. A ribbon is a zig zag folded ribbon that moves within a strong magnetic field, a principle also applied in ribbon microphones. That results in a sublime but vulnerable quality!

Initially he used the ribbons for higher frequencies, but realized that the crossover point at mid frequencies between ribbon and dynamic loudspeaker caused too many incurable difficulties. He strived for a full range ribbon loudspeaker but was not able to realize that. It than became clear to him that the electrostatic principle works with a moving mass comparable to that of air. and in practice the crossover between specific electrostatic units could easily be done with less side effects.

Original ESL 57

Newly built ESL’s by Quad Musikwiedergabe

The Quad electrostatic was in 1955, the year of introduction, the first full range electrostatic in the world. All others, like Janszen, made use of an extra bass speaker, just like nowadays Martin Logan, Solostatic en Final. Al combinations who were never convincing for my ears, even the combination with the Gradient subwoofer.

Many years ago, while listening alternatively on ESL 57 and AR 3A loudspeakers, a good business friend, the late loudspeaker manufacturer George Vermeulen suggested a trial to listen to his own design: a set of Quad’s 55 electrostatics, together with a Pioneer electronic crossover and two transmission line loudspeaker designed by him for the bass end. His proposal resulted in two 1,5 meter high transmission line towers, fitted with AR3A woofers. The designer suggested that crossover frequency should lie at 50 Hz and that the level of the low frequency units should be lowered to near inaudible during listening and that I would not be surprised that at the end of the listening sessions the woofers would be switched off. He was right! Sure, lots of music ask for more low end, but for serious listening to excellent recordings low frequency response can be troublesome. ESL’s lower frequencies may be limited but far more transparent than dynamic loudspeaker’s low frequency response. And mid frequency response stays in full bloom as far as electrostatics are concerned, not smeared by overkill of dynamic’s low frequencies and their harmonics. This I will always keep in mind and it became at that time already clear to me that ESL low frequency roll-off is strong, but favors strongly overall definition and transparency. Theoretically not a surprise but practically yes!

ESL 57’s strongest asset is the mid frequency response (around the human voice). Strings, voices and wind instruments are exemplarily reproduced and after more than 5 decades after its introduction. High frequency is somewhat capricious, greatly appreciated by many music lovers but an aspect that can irritate. The main disadvantage is not lack of low frequency response but the relatively narrow directivity pattern, which makes off- axis listening problematic. However these aspects have improved by the refurbished or newly built ESL’s from Quad-Musikwiedergabe. Even minor peaks in higher frequencies are straightened.
By the original version the high frequency impression changes by turning one’s head a little and that can be a nuisance. But it must be said that a dipole loudspeaker combined with a certain horizontal directivity makes the ESL concept less sensitive for problematic acoustic environments. Second advantage is the limited vertical dispersion that makes the speaker sounding less booming than others, caused by reflection right in front of the speaker. The limited dispersion for high frequencies made that I used the 55 as monitoring loudspeakers by recording classical music in churches and small halls. In rooms where one has never been before, electrostatic monitoring give less confusion than dynamic speakers.

Quad Musikwiedergabe took over the manufacturing tools from Acoustical Mfg Co. Ltd, Huntingdon, England. They build new electrostatic panels but make use of more devotion, better skills and better materials than ever before. And that is quite audible. Would you like to pay a visit to the German factory in the Eifel countryside, near Koblenz, we would recommend that very much: very nice people, fantastic area. But please make an appointment.

The ESL 57 is still, especially for chamber music and jazz, a more than eminent loudspeaker, cherished by many music lovers and rightly so. And luckily enough, the speakers can always be repaired or new built.

Quad Musikwiedergabe ESL 63 QA

The ESL 63 is quite another concept than the 57. The smart set up with concentric rings and their delay lines (explanation of the principle on this site) realise a outstanding dispersion and the neat construction results in the absence of small peaks in response, so characteristic for the 57. no wooden but a metal, rigid frame. And the Germans learned us that improving that rigidity gives even better results. Some - even avid music lovers - regard the 63 as a dull sounding speaker compared to the 57, just like some music lovers regard the 34 giving a more fresh sound than the 33. But: the more neutral, the more discreet, the symbol of quality.

Quad Musikwiedergabe ESL 63 QA

New built ESL 63 with metal chassis

ESL-63 in original outfit (choice of colours)

In 1981 when reviewing the ESL-63 I compared them with my own set ESL 57’s. My first impression was that the 63’s sounded somewhat dull en not spectacular. After six weeks of listening I connected my 57’s again and was astounded to realized the 57’s small peaks in frequency response compared to the 63 smooth performance. That the 63’s frequency response went a bit lower than that of 57 by a far better dispersion convinced me that I should exchange my old speakers for the new 63 set. I still am, although the by Quad Musikwiedergabe newly built 57’s perform on several aspects far more better than the original design. And for specific music – as said before - it still is – and stays a sublime transducer for intimate listening (chamber music, jazz, folk music, Lieder recital).
(via Quad Musikwiedergabe – zie ook website www.quad-musik.com)

To buy electrostatic loudspeakers

New electrostatic loudspeakers are not cheap, so it is tempting to look after second hands! But beware: because low standard production quality caused owners to sell the speakers. And repair costs are relatively high. In that case one could better buy by QUAD Musikwiedergabe or through us a pair of refurbished electrostatics than taking the risk of buying a defect pair and undertake refurbishing elsewhere.

It is also possible to buy newly built ESL 57 and ESL 63 speakers, build with better materials than ever before and built up with much more care than in the past. British ingenuity combined with dedicated German craftsmanship. Both designs are also available in a much improved version with a QA suffix. The ESL 63QA being the best sounding transducer I ever heard. See my review on this website.

Pitfalls
In fact it is a relatively a dangerous undertaking to buy a pair of second hand ESL’s as it is more than likely that you will be confronted with high repair costs. Because of the before mentioned mediocre production quality, damage occurs leading to replacement of the electrostatic units. Obvious is that replacement of one unit can lead to balancing problems with the other unit(s). The audible difference in sound balance makes relaxed listing difficult.

In most cases (ESL 55) the only reusable units are the wooden frame and the audio transformer. Of course there is always the opportunity to find a real good pair offered for sale by someone who inherited a set from a passed away uncle. But listen carefully to unwanted noises and rattles. By the ESL 63 a small rubber cap on the foot can be removed to observe the flickering of a small neon bulb. Optimum is a light signal once in 30 seconds. Does flickering occur far more, the high voltage for the stators is leaking. A torch is useful by inspection the dust covers of the electrostatic units, By the 63 the cloth needs to be pulled down, an easy job by removing (sliding to the right ) the wooden top panel of the loudspeaker.

For all electrostatics it is preferable to leave them connected to the mains supply - permanently. Power consumption is negligible. And keep in mind: switching a few times per day your power amplifier on and off doesn’t make the amplifier better and leaving it connected the whole day not worse.

Life expectancy
Electrostatics have a bad reputation as fare as reliability and maintenance are concerned, thanks to mediocre British production quality. Once thoroughly repaired with first class components results in years of trouble-free hi class listening.

The ESL 55 (57) has no amplifier protection whatsoever and can only be connected to a power amplifier of limited capacity. In contrast to normal dynamic loudspeakers an electrostatic high/midrange unit is instantly blown up by overload. The voice coil of a cone loudspeaker will heat up and eventually stops moving. A blown up electrostatic panel shows a corona on membrane and on one of the stators and after that incident every time annoying noises emanate from that unit. Electrostatic panels manufactured by Quad-Musikwiedergabe are not that sensitive for overload, as practice learns.

ESL 63 and successors are equipped with their own ‘crow bar’ protection. Short circuiting the input by massive overload as in general it is cheaper to repair power transistors than loudspeaker units.

Resumé
All parts including grills in every colour, wooden side panels, legs, cloth in all colours, are deliverable, see the Quad Musikwiedergabe website.